The present invention relates to a high-frequency wave supplying structure for supplying a high-frequency wave such as a microwave to a workpiece placed in a chamber.
Japanese Laid-Open Patent Publication No. 07-243035 discloses a film forming apparatus capable of performing, in a single chamber, a first process for depositing a metal film on a workpiece and a second process for forming a film on the workpiece by supplying high-frequency waves such as microwaves to the chamber.
Japanese Laid-Open Patent Publication No. 2006-83405 discloses a high-frequency wave supplying structure that supplies a microwave, which is an example of high-frequency wave, to a workpiece in a chamber. As shown in FIG. 7, the high-frequency wave supplying structure described in this publication includes a center conductor 101, which extends in a specified direction, a tubular outer conductor 102, which is arranged outward of the center conductor 101 and coaxial with the center conductor 101, and a cylindrical insulating member 103, which is arranged between the outer conductor 102 and the center conductor 101. The center conductor 101 protrudes from the opening of the outer conductor 102 located in the chamber 110. At the distal end of the center conductor 101, a support portion 104 for supporting a workpiece 150 is provided.
When a microwave is supplied to the center conductor 101, the microwave flows toward the support portion 104 through between the center conductor 101 and the outer conductor 102, that is, through the insulating member 103, as indicated by arrows in FIG. 7. The microwave is thus supplied to the workpiece 150. Then, in the vicinity of the workpiece 150 in the chamber 110, the microwave turns the process gas supplied to the chamber 110 into plasma to decompose the gas. The decomposed process gas adheres to the workpiece 150 so that a film made of the gas is formed on the workpiece 150.
When the first process is performed in the chamber of the film forming apparatus described in Japanese Laid-Open Patent Publication No. 07-243035, metal adheres not only to the workpiece but also to wall surfaces of the chamber and components in the chamber. For this reason, when employing the high-frequency wave supplying structure of Japanese Laid-Open Patent Publication No. 2006-83405 in the film forming apparatus of Japanese Laid-Open Patent Publication No. 07-243035, metal 160 adheres to a portion of the high-frequency wave supplying structure that is located in the chamber 110, and the metal 160 may connect the center conductor 101 to the outer conductor 102. In this case, if the outer conductor 102 is grounded, the high-frequency wave supplied to the workpiece 150 by the high-frequency wave supplying structure leaks to the outer conductor 102 via the metal 160. This hinders supply of the high-frequency wave to the workpiece 150.